WASHINGTON — The military scandal involving sharing of sexually explicit images of troops has expanded beyond the private social media site Marines United to a slew of gay pornography web pages with images of men wearing military uniforms engaged in sex acts, USA TODAY has learned.

The broadened investigation to an increasing number of websites underscores the complexity of policing social media sites where sensitive images can be uploaded in an instant for all to see. In the case of the sites with gay pornography, military investigators will be tasked with determining whether active-duty troops were involved in conduct that could bring discredit on their service, a potential violation of military law.

The Marine Corps is not the only service affected. Images of men in the uniforms of sailors, soldiers and airmen also appear on an array of Tumblr sites. Similar to the Marines United case, it is unclear whether men appearing in the images — some photographed engaging in sex — provided consent to have their images shared publicly. Victims of so-called revenge porn in the Marines United case have limited protection under military law if the photographs or videos were taken originally with their consent.

The Pentagon has established a joint military task force to handle the growing investigation, said MaryAnn Cummings, a spokeswoman for the Naval Criminal Investigative Service.

Navy, Marine, Army, Air Force and Coast Guard investigators have "established a multi-service task force to expand the investigation," she said.

Military officials briefed Congress on Thursday about the Marines United scandal, in which hundreds of active-duty Marines have viewed photos of servicewomen taken without their consent and cyberbullied some of them.

On some of the gay Tumblr sites, fully dressed troops appear in photos with their name tags visible. At least one such Marine did not agree for his photo to be republished amid a sea of images of men having sex, according Lt. Col. Eric Dent, a Marine Corps spokesman.

Air Force investigators also are now combing through a number of websites to look for victims, said Col. Pat Ryder, an Air Force spokesman.

“The Air Force Office of Special Investigations is investigating information and photographs from web sites hosting inappropriate photos of service members without prior consent,” Ryder said. “As part of that ongoing criminal investigation, airmen identified will be contacted directly by AFOSI to determine whether they are victims.”

Determining whether the men in the photos, many involved in group sex, are active-duty troops is possible, said a congressional source on a military oversight committee who was not authorized to speak publicly about the issue. NCIS has dedicated dozens of investigators to the matter, the source said. They can comb through the photos and identify troops with the use of facial-recognition software.

The revelation of the expanded investigation drew swift response from Capitol Hill. Sen. Kirsten Gillibrand, a New York Democrat and member of the Armed Services Committee, called on Congress to intervene. Earlier this week, she blasted Marine and Navy officials for failing to hold commanders accountable for the problem.

"This scandal is out of control and the Department of Defense needs to get a handle on it immediately," Gillibrand told USA TODAY in a statement. "Congress needs to demand accountability from the chain of command as to how so many service members, both women and men now, could be so easily exploited. Commanders have told us for decades that they can handle these issues, clearly they cannot, and Congress should step up and do its job and bring professionalism and accountability to the military justice system that has ignored predators for far too long.”

Marine Corps Commandant Gen. Robert Neller told the Senate this week that Marines need "to commit to get rid of this perversion to our culture."

Punishment, including court martial, is possible if active duty troops can be identified on the pornographic websites, said Don Christensen, president of Protect Our Defenders, an advocacy organization for victims of sexual abuse in the military.

Precedent exists for booting troops from the ranks for posing nude in men’s magazines, said Christensen, who was also the top prosecutor for the Air Force. Court martial would be possible for troops who posted images of themselves in uniform exposing themselves or having sex.

There is a defense for free speech and freedom of expression, he said. But the military has wide latitude in disciplining or dismissing troops for conduct that affects good order and discipline. Photos such as these, he said, certainly fill that bill.